Post-processing apparatus and image forming system

ABSTRACT

The post-processing apparatus obliquely disposed is provided with a stacker  21  to stack a recording sheet bundle S, a stopper  22  located at a lower end D of the stacker  21  and a blower section  3  disposed at the lower end D side of the stacker  21.  The recording sheet bundle S is conveyed to the stacker  21  via a conveyance path a. The blower section  3  blows air towards a lower edge SD of the recording sheet sliding down on the stacking surface P of the stacker  21  from an upper end U side to the lower end D side of the stacker  21.

This application is based on Japanese Patent Application No. 2010-293043 filed on Dec. 28, 2010, in Japanese Patent Office, the entire content of which is hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to a post-processing apparatus to apply post-processing to a recording material conveyed from an image forming apparatus and an image forming system.

BACKGROUND OF THE INVENTION

At a subsequent stage side of the image forming apparatus such as a copying machine and a digital multifunction peripheral (MFP), a post-processing apparatus is connected. In case post-processing such as bookbinding is applied, it is necessary to register lateral and longitudinal edge sections of a sheet bundle (bundle of the recording material) i.e. to align the sheets before the post-processing.

Generally the post processing apparatus is provided with a stacker disposed obliquely with respect to the horizontal plane (a installation surface of the post-processing apparatus), and is configured so that the sheets (recording materials) conveyed from the image forming apparatus are stacked sequentially on a stacking surface of the stacker by it's own weight. The sheets conveyed from the image forming apparatus are brought into the stacking surface of the stacker and subsequently slide down along the stacking surface of the stacker by free fall then lower edges of the sheets come to contact with a stopper disposed at a lower end of the stacker to be aligned as a sheet bundle.

However, in some cases, register of the edge sections of the sheets in an ejection direction particularly by a free fall method, where the sheet edges are registered by free fall of the sheets, is incomplete due to an effect of a friction between a sheet already stacked on the stacker and a sheet to be stacked subsequently.

Also, there is a case that by stacking several sheets at an upstream side of the stacker in a sheet conveyance direction in advance, the sheets are brought into the stacker at one time to improve productivity. In the above case, register of the sheets may be incomplete only by the free fall method, if the sheets stacked in advance stick each other and cannot be separated even on the stacker.

To solve the above problem, a post-processing apparatus having a mechanism to register the sheets by beating the edge sections of the sheets after a plurality of the sheets are stacked on the stacker is disclosed in Patent Document 1: Unexamined Japanese Patent Application Publication No. 2003-192213.

Patent Document 1: Unexamined Japanese Patent Application Publication No. 2003-192213

SUMMARY

However, according to Patent Document 1, to register the edge sections of the sheets in the ejection direction, a sheet front edge bias member has to be pressed against a front edge of the sheet bundle. Thus to register a large size sheet bundle, for example, A3 sheet bundle (297 mm×420 mm), size of the stacker, in particular a length in an oblique direction of the stacker, has to be extended since the movable range of the sheet front edge bias member has to be enlarged, which is an obstructive factor for downsizing and cost reduction of the post-processing apparatus. Further, depending on the type of sheet, or environment, in case the sheets stick each other, register may be incomplete even if the sheet front edge bias member is pressed against the front edge of the sheet bundle.

The present invention has one aspect to solve the above problems and an object of the present invention is to provide a post-processing apparatus and an image forming system to enhance accuracy of register of the recording material bundle. To achieve the above object, the post-processing apparatus and the image forming system reflecting one aspect of the present invention comprises the following structures:

-   Structure 1. A post-processing apparatus, comprising: a stacker     obliquely disposed to stack a recording material bundle; and a     blower section disposed at a lower end side of the stacker to blow     air from the lower end side to an upper end side of the stacker     towards an edge section of a recording material being sliding down     on a stacking surface of the stacker. -   Structure 2. The post-processing apparatus of structure 1, further     comprising a stopper to contact with an edge section of the     recording material bundle to be stacked on the stacking surface,     wherein the blower section continues to blow air within a time     period from when the recording material is conveyed to the stacker     to at least when the edge section of the recording material comes in     contact with the stopper. -   Structure 3. The post-processing apparatus of claim 1, further     comprising a control section to control the blower section so as to     blow air in a case when a recording material size exceeds a standard     size. -   Structure 4. The post-processing apparatus of structure 1, further     comprising a control section to control the blower section so as to     blow air in accordance with type, basis weight, number or size of     the recording material. -   Structure 5. The post-processing apparatus of claim 1, further     comprising a push down member supported in a rotatable manner around     an axis to push down a rear edge of the recording material to be     conveyed to the stacker towards the stacking surface. -   Structure 6. The post-processing apparatus of structure 1, further     comprising a post-processing section to apply post-processing to the     recording material stacked on the stacker. -   Structure 7. An image forming system, comprising: an image forming     apparatus to from an image on the recording material, and the post     processing apparatus of structure 1 to convey the recording     material, on which the image has been formed by the image forming     apparatus, and to apply post-processing to the recording material.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an external view showing an exemplary configuration of an image forming system 100 related to an embodiment of the present invention.

FIG. 2 is a diagram showing an exemplary configuration of relevant parts of a post-processing apparatus FS related to an embodiment of the present invention.

FIG. 3 a schematic diagram to explain a case that an edge section of a large sheet bundle in a sheet ejection direction is registered using a blower 3 related to an embodiment of the present invention.

FIG. 4 is a perspective view of a sheet stacking section 2 and a blower section 3 related to embodiments of the present invention.

FIG. 5 is a diagram schematically showing a structure of a cross-section between X1 to Z2 shown by FIG. 4.

FIG. 6 is a block diagram exemplifies a control system 6 related to an embodiment of the present invention.

FIG. 7 is a flow chart showing an exemplary control of a control system 6 related to an embodiment of the present invention.

Embodiments of the present invention will be described with reference to the drawings as follow.

<Exemplary Configuration of Image Forming System 100>

FIG. 1 is an external view showing an exemplary configuration of an image forming system 100 related to an embodiment of the present invention. The image forming system 100 includes an image forming apparatus A and a post-processing apparatus FS (Finishing Apparatus). The image forming apparatus A is provided with an automatic document feeding apparatus) ADF to convey a document to a scanning section (unillustrated) and an operation display section O to prompt a user to operate and to accept operation of the user.

The image forming apparatus A is a digital multifunction peripheral enables monochrome and color printing by an electrophotographic method. In the present embodiment, while the image forming apparatus A will be described as an apparatus using the electrophotographic method, it can be an apparatus using another image forming method such as an inkjet method.

The image forming apparatus A creates image data of the document by scanning the document conveyed to the scanning section through the automatic document feeding apparatus ADF. Basically the image forming apparatus A forms an image of the image data on a sheet by sequentially conducting charging processing, exposing processing, developing processing, transfer processing and cleaning processing. The image forming apparatus A conveys the sheet on which the image is formed to the post-processing apparatus FS.

The post-processing apparatus FS conducts “a sheet bundle forming process” to form a sheet bundle as the post-processing by sequentially brought in the sheets from the image forming apparatus A. At the sheet bundle forming process, the post-processing apparatus FS aligns the sheet bundle. The post-processing apparatus FS applies a binding process by a stapler to the sheet bundle aligned and ejects the sheet bundle to a sheet ejection tray T. As the post-processing, besides the above, “perforation processing” to from a hole at a given position on the sheet, “folding processing” to fold the sheet, and “gluing and bookbinding processing” to apply a glue are cited. The post-processing conducted by the post-processing apparatus FS is selected by an instruction of the user using the operation display section O or in case the image forming apparatus is connected via network, the post processing is designated by an external equipment such as a PC. In the present embodiment, the sheet bundle forming processing will be described.

<Exemplary Configuration of Post Processing Apparatus FS>

An exemplary configuration of the post-processing apparatus FS will be described. FIG. 2 is a diagram showing an exemplary configuration of relevant parts of the post-processing apparatus FS related to an embodiment of the present invention. The post-processing apparatus FS is provided with a sheet introducing section 1, a sheet stacking section 2, a blower section 3, a sheet ejection section 4 and an ejected sheet tray T.

The sheet conveyance section 1 is provided with a pair of introducing rollers RE At the sheet introducing section 1, the pair of the introducing rollers R1 nips the sheet ejected from the image forming apparatus A. The sheet introducing section 1 conveys the sheet to the sheet stacking section 2 as the conveyance path a shows.

The sheet stacking section 2 is provided with a stacker 21 to stack the sheet. The stacker 21 is disposed with an ascending vertical angle with respect to a horizontal plane HP on which the post-processing apparatus is installed.

In the sheet stacking section 2, the sheets brought in via the conveyance path are stacked on the stacker up to a designated number of the sheets so as to from an aligned sheet bundle. The sheet stacking section 2 discharges the sheet bundle on the stacker 21 to the sheet ejection section 4 after the bookbinding section (Refer to FIG. 4) applies the bookbinding processing to the sheet bundle.

The blower section 3 is disposed at a lower end side of the stacker 21 along the oblique direction of the stacker 21. The blower section 3 blows air towards an upper end side from the lower end side of the stacker 21.

The sheet ejection section 4 is provided with a pair of ejection rollers R2. At the sheet ejection section 4, the pair of the ejection rollers R2 nips the sheet bundle discharged from the sheet stacking section 2 to eject the sheet bundle onto the ejected sheet tray T.

The ejection sheet tray T can move up and down in a vertical direction with respect to the horizontal plane HP. The ejected sheet tray T stores the sheet bundle ejected from the sheet stacking section 2.

The post-processing apparatus FS can form a plurality of booklets continuously by applying binding processing to the sheet bundles having a designated number of the sheets (for example, 10 pieces). The binding processing is cathed out in a state where the sheet bundle is stacked on the stacker 21. Therefore, in a time period in which the binding processing is carried out, the stacker 21 cannot stack new sheets on the sheet bundle already present though the new sheets are conveyed from the image forming apparatus A to the post-processing apparatus FS.

Therefore, in the time period in which the binding processing is cathed out, the post-processing apparatus FS temporally stores and stacks several sheets introduced in the above period in another sheet accumulating device (unillustrated) disposed at an upstream side of the sheet stacking section 2 in the sheet conveyance direction. After the bookbinding processing is completed and the sheet bundle is ejected to the ejected sheet tray T by the sheet stacking section 2, the post processing apparatus FS conveys the sheets temporally stored to the sheet stacking section 2. The sheet stacking section 2 stacks subsequent sheets newly conveyed to configure the same booklet onto the sheet bundle of several sheets. A case that a sheet bundle in which several sheets are stacked is conveyed to the stacker 21 will be exemplified as follow.

In the present embodiment, the blower section 3 is used in case that an edge section of, in particular, a large sheet bundle (for example, A3 sheet), in the ejection direction is to be registered. The above will be described as follow. FIG. 3 is a schematic diagram to explain that the edge section of the large size sheet in the ejection direction is registered using the blower section 3 related to the embodiment of the present invention.

The sheet stacking section 2 is provided with a stopper 22 located at a lower end D of the stacker 21 and a pair of conveyance rollers 29 a and 29 b. The stopper 22 contacts with the lower edge SD of the sheet bundle S at the lower end D of the stacker 21 in a longitudinal direction of the stacker 21.

The sheet bundle S configured with several sheets grasped by the conveyance rollers 29 a and 29 b via the conveyance path a is conveyed to the stacker 21. The sheet bundle S falls towards the stacking surface P of the stacker 21 by its own weight and slides on the stacker 21 then stops at the stopper 22. Depending on the size and kind of the sheet, in case the sheets are sticking each other in the sheet bundle S conveyed to an upper portion of the stacker 21, it may be difficult to register the sheet bundle S.

As an arrow F shows, the blower section 3 blow air towards an upper end U from the lower end D of the stacker 21. Then, air penetrates between surfaces of the sheets (hereinafter simple called sheet surface gap) and a thin air layer is formed in the sheet surface gap and the sheets are separated each other. Thereby, since each sheet can move freely, the sheet bundle S is registered at a position of the lower edge SD when the sheet bundle S slides toward the stacking surface P of the stacker 21 and slides on the stacking surface P then comes in contact with the stopper 22. If the size of the sheet is large, the weight thereof is also large, thus registration of the sheet bundle S at the lower end SD can be carried out easily without using the registration member 24 (refer to FIG. 5) to be described.

<Exemplary Configuration of Sheet Stacking Section 2>

An exemplary configuration of the sheet Stacking Section 2 will be described. FIG. 4 is a perspective view of the sheet stacking section 2 and the blower section 3 related to the embodiment of the present invention. In FIG. 4 a binding section 5 to conduct the binding process is also shown.

Incidentally, an X axis indicates a direction perpendicular to the sheet ejection direction and parallel to the stacking surface. An Y axis indicates the sheet ejection direction. A Z axis shows a direction perpendicular to the X and Y axes.

The sheet stacking section 2 is provided with a sheet ejection belt 23, a registration member 24, a first registration member 25R and a second registration member 24L, a flap 26 and a shaft 27.

Stacker 21 is configured with a first guide plate 21R, and a second guide plate 21L. The first guide plate 21R, and the second guide plate 21L are substantially in shapes of rectangles respectively. The first and second guides are disposed parallel to each other and separated in the X direction with a gap in which an ejection belt 23 rotates in the Y direction. The stacker 21 can be formed as a single piece. The stacker 21 stacks the sheets conveyed onto the stacking surface P.

The stopper 22 is provided with a first stopper member 22R and the second stopper member 22L. The first stopper member 22R is extending from the lower end D of the first guide plate 21R for a given distance and then extending in a positive direction of the Z axis. The first and second stopper members 22R and 22L are separated in parallel to the X direction with a distance which is wider that a width of the ejection belt 23. The stopper 22 receives the sheet sliding on the stacking surface P of the stacker 21 in the oblique direction (negative direction of the Y axis).

The ejection belt 23 is supported by a first drive pulley 210 and a second driven pulley 211 which are disposed to be distant in the Y axis direction between the first and the second guide plates 21R and 21L. The ejection belt 23 moves along the Y axis by rotation of the first drive pulley 210 and the second driven pulley 211.

As viewed from the Y axis direction, the registration member 24 is a rectangle or a substantially rectangle member having a long side which is perpendicular to the ejection belt 23. A bottom section of the registration member 24 is fixed onto the ejection belt 23. The width of the registration member 24 is slightly wider than the width of the ejection belt 23. The width of the registration member 24 can be the same or substantially the same as that of the ejection belt 23.

The registration member 24 has two functions. A first function relates to registration of the sheet bundle. The registration member 24 moves from a stand-by position downward (negative direction of the Y axis) along with a positive rotation of the ejection belt 23 when a designated number of the sheets are stacked on the stacker 21. The positive rotation as used herein refers to a clockwise rotation direction on a Y-Z plane as viewed from the negative direction of the X axis. The registration member 24 presses lightly a front edge of the sheet bundle to register the edge section of the sheet bundle in a longitudinal direction. Hereinafter, the longitudinal direction denotes a direction (ejection direction) indicated by the positive direction of the Y axis.

Basically, registration of the edge section of the sheet bundle in the longitudinal direction using the registration member 24 is conducted when the sheet size is smaller than a standard size. In the present embodiment, for example, A4 size (210 mm×297 mm) is a standard size. The reason for the above is that, for example, since a sheet of A6 size (105 mm×148 mm) smaller than A4 size sheet is lighter that the A4 size sheet, the A6 size sheet can be blown off by the air blow of the blower section 3, therefore the registration member 24 is used to register the small size sheets.

A second function is a function to eject the sheet bundle. The registration member 24 moves from the stacking surface P side of the stacker 21 to the rear edge of the sheet bundle via an reverse surface side. The registration member 24 presses the rear edge of the sheet bundle with an opposite surface to the pressing surface so as to push up the sheet bundle towards the ejected sheet tray (Refer to FIG. 2).

The first and the second width aligning members 25R and 25L are disposed in parallel to each other. The first and the second aligning members 25R and 25L move in an opposite direction each other along the X axis by the same distance. A moving mechanism is provided with a rotation belt 251 disposed along the X axis direction at a lower section of the stacker 21 and a second drive pulley 252 suspending the rotation belt 251 to drive and rotate the rotation belt 251 (refer to FIG. 6). The movable range of the first and the second width aligning members 25R and 25L depends on the size of the sheet stacked on the stacker 21.

When the sheets of designated number are stacked on the stacker 21, the first and second aligning members 25R and 25L press the sheet bundle from both sides edge to align the edge section of sheet bundle in a lateral direction. Hereinafter, the lateral direction refers to a perpendicular direction with respect to the ejection direction.

The flap 26 representing the pressing down member lightly presses down a vicinity of the rear edge of the sheet conveyed from the stacker 21 towards the stacking surface P of the stacker 21 so as to serve a function to fall the sheet rapidly onto the stacking surface P of the stacker 21. The flap 26 is a member in as shape of a wing which crosses the stacker 21. A shape of a cross-section of the flap 26 can be, for example, a wedge shape or a plate shape. A side edge of the flap 26 in a positive direction side of Y axis, specifically a thicker side edge, is connected with the shaft 27. On stand-by, as FIG. 4 shows, a surface of the flap 26 in a longitudinal direction locates in parallel or substantially parallel with respect to the stacking surface P of the stacker 21.

The shaft 27 is connected with, for example, an (unillustrated) transmission mechanism such as a gear train at an end. The shaft 27 rotates via the transmission mechanism when a fourth drive motor M4 (refer to FIG. 6) rotates.

<Exemplary Configuration of Blower Section 3>

An exemplary configuration of the blower section 3 will be described. The blower section 3 is provided with a supporting bracket 31. The blower section 3 is, for example, a blower to blow air. The blower section 3 rotates a fun (unillustrated) to generate an air flow.

On/off and an amount of air blow of the blower section 3 is controlled by a control section 64 (refer to FIG. 6). The air blow section 3 is turned off at an initial state and switched from off to on so as to blow air in a time period of forming the sheet bundle when the sheet bundle in which several sheets are stacked is brought into the stacker 21 and in case the sheet size is larger than the standard size. Incidentally, if an air blow amount to enable forming of the air layer in the sheet surface gap can be obtained, the blower can be substituted by a fan.

The blower section 3 is located in a position where air exhausted can flow from the lower end D to the upper end U of the stacker along the stacking surface P. Specifically, the air blower section 3 is located at a position which is a predetermined distance away from the lower end D of the stacker 21 on a straight line in the negative direction of the Y axis.

In order to create the air layer between the sheet surfaces, an appropriate amount of blowing air not to blown off the sheet is necessary. If the air amount of the blower section 3 is too small, the air layer cannot be formed between the surfaces of the sheets. On the other hand, if an outlet of the blower section 3 is too close to the lower end D of the stacker 21, the sheet is blown off even if the air blow amount is set at a minimum amount. Therefore, in the present embodiment, for example, the outlet is located at a position which is approximately a width of the stapler 5 in the negative direction of Y axis away from the stopper 22 located at the lower end D of the stacker.

The amount of the blower section 3 will be described. Basically, as the number of the sheets stacked increases, an amount of the air blow from the blower 3 is increased. In accordance with the type, basis weight, weight and size of the sheet, the air blow amount can be adjusted as follow.

For example, in case the surface of the sheet is coated as the coated sheet, the air from outside is difficult to penetrate when the air layer between the surfaces of the sheets is lost by a moisture absorption action thus the sheets tends to sticks each other. Thus when the coated sheet is used, it is preferred to increase the amount of air blow compared to a case where non-coated sheets are used.

As the weight or basis weight increases, namely as the thickness of the sheet increases, the amount of air blow is increased. In the same manner, as the size of the sheet increases, the amount of air blow is increased.

The support bracket 31 is a bracket to adjust the position of the air blower section 3 so that the air discharged from the air blower section 3 flows along the stacking surface P from the lower end D to the upper end U. Incidentally, the height and the position of the support bracket 31 are determined preferably at the planning stage.

<Exemplary Configuration of Bookbinding Processing Section 5>

An exemplary configuration of a bookbinding processing section 5 will be described. The bookbinding processing section 5 is provided with a stapler 51 representing a binding device. The bookbinding processing section 5 is provided with a shaft 52, a belt 53 and a third drive pulley 54 (Refer to FIG. 6) as moving mechanisms of the stapler 51.

The stapler 51 reciprocates along the shaft 52 by rotation of the belt disposed in the X axis direction beneath the stapler 51. The stapler 51 moves to a designated position (for example, a corner of the sheet bundle) of the sheet bundle to be bound from a stand-by position (supposing that X=X1) shown by FIG. 4, and binds the sheet bundle at the above position. Number of the binding positions can be one or more than one.

The shaft 52 penetrating through an opening section 511 of a mount of the stapler 51 supports the stapler 51 so as to move the stapler 51 in the X axis direction.

The belt 53 is suspended rotatably via a third pulley 54 (Refer to FIG. 6) and a pulley 55 located at a position opposite to the third pulley 54 in the X axis direction.

The third pulley 54 is driven and rotated by the third motor M3 (refer to FIG. 6). The third pulley 54 drives the pulley 55 by rotating the belt 53 and reciprocates the stapler 51 along the shaft 52. <Outline of Operation of Post-Processing Apparatus>

Outline of operation of the post-processing apparatus will be described. FIG. 5 is a diagram schematically showing a configuration of a cross-section X1-X2 shown by FIG. 4. The sheet stacking section 2 is provided with a sensor section 28, a pair of conveyance rollers 29 a and 29 b, a first drive pulley 210 and a second driven pulley 211.

The pair of the conveyance rollers 29 a and 29 b convey the sheet bundle S via the conveyance path a to the stacker 21.

The stacker 21 stacks the sheet bundle S of several sheets conveyed via the conveyance path a on the stacking surface P.

The sensor section 28 is configured with an infrared ray sensor and so forth. The sensor section 28 detects passing of the sheet bundle S conveyed through the conveyance path a at a vicinity of a conveyance roller 29 c. When passing of the sheet bundle S is detected, the sensor section 28 outputs a detection signal to notify the passing to a control section 64 (refer to FIG. 6) via a input/output section 63. The installation position of the sensor section 28 is, for example, between the conveyance roller 29 c and the pair of the conveyance rollers 29 a and 28 b on the conveyance path a, when the sheet bundle S can be detected on the conveyance path a before the sheet bundle S reaches to the flap 26.

The flap 26 is disposed at an upper end U side of the stacker 21 with respect to the pair of the conveyance rollers 29 a and 29 b in the extending direction of the stacking surface P. The flat 26 is in a stand-by position shown by FIG. 5 at a initial state. When the sensor section 28 detects entering of the sheet and a vicinity of the rear edge SD of the sheet bundle S having passed through the pair of the rollers 29 a and 29 b reaches at the flap 26, the shaft 27 rotates in a positive direction by the sensor's detection as a trigger. By positive rotation of the shaft 27, the flap 26 rotates in the positive direction up to a given position shown by a two-dot chain line in FIG. 5 from the stand-by position. In the present embodiment, the given position of the flap 26 is a position when the flap 26 becomes substantially parallel to the stacker 21.

The sheet bundle S passed through the pair of the rollers 29 a and 29 b is lightly pressed downward towards the stacking surface P of the stacker 21 by the flap 26 at the rear edge SD and falls towards the stacking surface P. A conveyance path al shown by a solid line in FIG. 5 shows a path through which the sheet bundle S whose rear edge SD is pressed by the flap 26 goes through. On the other hand, a conveyance path a2 shown by a one-dot chain line in FIG. 5 shows a virtual path which the sheet bundle S pursues in case the flap 26 does not operate. By the flap 26 to press the rear edge SD of the sheet bundle S, the sheet bundle S can fall rapidly onto the stacking surface P of the stacker 21 without the sheet being blown by the blow air of the blower section 3.

When the sheet bundle S falls on the stacking surface P and the sheet bundle S slides on the stacking surface P then stops at the stopper 22 as the conveyance path a3 shows, the shaft 27 rotates in the negative direction. By the rotation of the shat 27 in the negative direction, the flap 26 returns from the given position to the stand-by position. In the present embodiment, while the flap 26 rotates in the positive direction from the stand-by position until it becomes substantially parallel to the stacker 21, it can rotate in the positive direction until a front end of the flap 26 becomes perpendicular to the stacker 21 while pressing down the rear edge SD of the sheet bundle S.

Incidentally, the first drive pulley 210 rotates in the positive or the negative direction by rotation drive of the first drive motor M1 (refer to FIG. 6) to drive and rotate the sheet ejection belt 23 and the driven pulley 211.

Whereby, the registration member 24 on the sheet ejection belt 23 moves to register and convey the sheet bundle S.

As an arrow F shows, the air blower section 3 blows air along the stacking surface P from the lower end D to the upper end U of the stacker 21. When this occurs, since it is necessary to form the thin air layer between the surfaces of the sheets, the blower section 3 continues air blow at least in a time period from bringing the sheet bundle S in the stacker 21 until the sheet bundle S slides on the stacking surface P and the rear edge SD of the sheet bundle S comes in contact with the stopper 22. Incidentally, while the air blower section 3 is blowing air, since the bookbinding process is in a halting state, the stapler 51 shown in FIG. 4 is in the stand-by position where the air blown by the air blower section 3 does not go through. Therefore, the air discharged from the air blower section 3 flows from the lower end D to the upper end U of the stacker 21 without being interrupted by the stapler.

<Control System to Control Sheet Stacking Section and Air Blower Section 3>

A control system to control the sheet stacking section 2 and the air blower section 3 will be described. FIG. 6 is a block diagram exemplifying a control system 6 related to an embodiment of the present invention. The control system 6 is provided with a RAM (Random Access Memory) 61, a ROM (Read Only Memory) 62, an input/output section (I/O) 63 and a control section 64. The control system 6 serves as a computer to control operation of the sheet stacking section 2. Incidentally, in the present embodiment, while each component of the control system 6 is disposed in the post-processing apparatus FS, they can be disposed in the image forming apparatus A.

The RAM 61 is a work area of the control section 64. The ROM 62 stores a control program to control operation of the sheet stacking section 2.

The input/output section 63 receives and transmits data between the sensor section 28 as well as the operation display section 0, and the control section 64.

The control section 64 is configured with, for example, a CPU (Central Processing Unit). The control section 64 reads out the control program from the RAM 61 to conduct the following control in accordance with procedures of the control program.

Firstly, the control section 64 acquires the size and type of the sheet from an instruction of a user inputted through the control display section 0. Also the control section 64 acquires number of the sheet stacked when the sheets are conveyed to the sheet stacking section 2. Then the control section 64 controls on/off and the air blow amount of the blower section 3. Secondary, the control section 64 judges whether the number of the sheets conveyed to the sheet stacking section 2 reaches to a given number for one booklet. Thirdly, the control section 64 controls first drive motor M1 to the forth drive motor M4.

The firs drive motor M1 rotates the first drive pulley 210 in the positive rotation direction or the negative rotation direction in accordance with control of the control section 64.

The second drive motor M2 is, for example a stepping motor”. The second drive motor M2 rotates the second drive pulley 252 in the positive or the negative rotation direction in accordance with control of the control section 64.

The third drive motor M3 rotates the third drive pulley 54 in the positive or the negative rotation direction in accordance with control of the control section 64.

The fourth drive motor M4 rotates the shaft 27 in the positive or the negative rotation direction in accordance with control of the control section 64.

<Exemplary Operation of Sheet Stacking Section 2 and Blower Section 3>Operation of the sheet stacking section 2 and the blower section 3 will be described. FIG. 7 is a flow chart showing an exemplary operation of the sheet stacking section 2 and the blower section 3 related to an embodiment of the present invention. In an initial state, the blower section 3 is off and the flap 26 is in the stand-by position.

(Step ST1)

The control section 64 acquires the number of the sheets stacked when the sheets are conveyed to the sheet stacking section 2. In case the number of the sheet stacked is more than 1 (YES), the operation proceeds to Step ST2. On the other hand, no sheet is stacked (NO), the operation proceeds to Step ST4.

(Step ST2)

The control section 64 judges whether or not the sheet size is larger than the standard size. In case the sheet size is larger than the standard size (YES), the operation proceeds to Step ST3. On the other hand, incase the sheet size is smaller that the standard size (NO), the operation proceeds to Step ST4.

(Step ST3)

In case the number of the sheets is more than 1 and the sheet size is larger than the standard size, the control section 64 switches the blower section 3 from off to on. Further, the control section 64 acquires the sheet size from the instruction of the user inputted from the operation display section O, and based on the above information and the number of the sheets stacked when the sheets were conveyed to the sheet stacking section 2, the control section 64 adjusts the air blow amount of the blower section 3. When the blower section 3 blows air in accordance with the air blow amount controlled by the control section 64, the air flows along the stacking surface P from the lower end D to the upper end U of the stacker 21. Incidentally, the control section 64 can further adjust the air blow amount of the blower section 3 in accordance with the type, weight and basis weight of the sheet

(Step ST4)

At least in case the sheets are not stacked or the sheet size is smaller than the standard size, the control section 64 keeps the blower section 3 being off.

(Step ST5)

In the initial state, the aligning member 24 is at the stand-by position. As the conveyance path a shows (refer to FIG. 5), the sheet stacking section 2 conveys the sheet bundle S in which more than one sheets are stacked via the pair of the conveyance rollers 29 a and 29 b. Since the blower section 3 is turned on, air penetrates into the gap between the sheet surfaces and the thin air layer is formed between the sheet surfaces.

(Step ST6)

In Step ST5, the sensor section 28 detects passing of the sheet coming through the conveyance path a at the vicinity of the conveyance roller 29 c. The sensor section 28 outputs a detection signal to notify passing to the control section 64. When the detection signal from the sensor section 28 is received, the control section 64 rotates the third drive motor M3 in the positive rotation direction after an interval in which the vicinity of the rear edge SD of the sheet reaches to the flap 26. Then the shaft 27 rotates in the positive rotation direction and the flap 26 rotates in the positive rotation direction from the stand-by position to the given position. The vicinity of the rear edge SD of the sheet bundle S is pushed lightly by the flap 26 towards the stacking surface of the stacker 21, then the sheet bundle S falls towards the stacking surface P of the stacker 21.

(Step ST7)

The control section 64 controls the second drive motor M2 to rotate the second drive pulley 252 so that the first and the second width aligning members 25R and 25L approach each other in a level that they push down the both side edges of the sheet bundle S. Whereby, the first and the second width aligning members 25R and 25L push down the both side edges of the sheet bundle S on the stacker 21. In Step ST7, the edged section of the sheet bundle S in the lateral direction is aligned.

(Step ST8)

In case the sheet size exceeds the standard size (YES), the sheet bundle S, in a state that the air layer is formed in the gap between the sheet surfaces by the air blow from the blower section 3, slides down on the stacking surface P by the gravity, and by an impact when the edge section of the sheet bundle S hits the stopper 22, the sheets are registered in the longitudinal direction. Therefore, in the above case, the operation proceeds to Step ST 9 without carrying out registration of the edge section of the sheet bundle in the longitudinal direction by the aligning member 24. On the other hand, in case that the sheet size is smaller than the standard size (NO), operation proceeds to Step ST10 so as to carry out registration of the edge section of the sheet bundle in the longitudinal direction by the aligning member 24.

(Step ST9)

In case the sheet size is larger than the standard size, the control section 64 judges whether or not the number of the sheets conveyed to the sheet stacking section 2 has reached to the designated number to configure the one booklet. In case the number of the sheets has reached to the designated number (YES), the operation proceeds to Step ST11. On the other hand, in case the number of the sheets has not reached to the designated number (NO), the operation proceeds to Step ST1.

(Step ST10)

In case the sheet size is smaller than the standard size, the aligning of the edge section of the sheet bundle in the longitudinal direction is carried out using the aligning member 24. The control section 64 controls the first drive motor M1 to rotate the first drive pulley 210 in the positive rotation direction so that the aligning member 24 contacts with the front edge section of the sheet bundle S and presses down the sheet bundle S lightly. Thereafter, the sheet ejection belt 23 rotates in the positive rotation direction and the aligning member 24 moves from the stand-by position in the negative direction of the Y axis. When the pressing surface of the aligning member 24 pushes down the front edge section of the sheet bundle S lightly, the rear edge section SD of the sheet bundle S comes to contact with the stopper 22. Thus in Step ST10, the edge section of the sheet bundle S in the longitudinal direction is aligned.

(Steps ST11 and ST12)

In the binding process, if the air layers are formed in the gaps between each sheet surface, the edge section on the binding side of the sheet bundle already registered may flutters. Therefore, before the binding process, in case the blower section 3 is on (YES), the control section 64 switches the blower section 3 from on to off so as to cease air blow (Step ST12). On the other hand, in case the blower section 3 is off (NO), the operation proceeds to Step ST13.

While the bower 3 is being turned off, the control section 64 rotates the third motor M3 to move the stapler 51 to the designated position. The stapler 51 binds the sheet bundle S at the designated position.

(Step ST14)

The control section 64 controls the first drive motor M1 to move the aligning member 24 as follow. Here, the aligning member 24 is supposed to be the stand-by position shown by FIG. 5. The control section 64 rotates the first pulley 210 in the negative rotation direction to move the aligning member 24 to the rear edge SD of the sheet bundle S via a reverse surface side of the stacker 21. Further, the control section 64 rotates the first drive pulley 210 in the negative rotation direction so as to move the aligning member 24 from the lower end D of the stacker 21 to the stand-by position.

When the aligning member 24 reaches to the lower end D of the stacker 21 via the reverse surface side of the stacker 21 from the stand-by position, the aligning member 24 pushes up the rear edge SD of the sheet bundle S remaining stationary by the stopper 22 in the Y direction and holds it. Then the aligning member 24 pushes up the sheet bundle S being held towards the upper end U of the stacker 21 to the stand-by position. Then in Step ST 14, the sheet bundle S is ejected to the ejected sheet tray T via the ejection rollers R2.

According to the present embodiment, if the sheet size is larger than the standard size, the blower section 3 blow air from the lower end D side to the upper end U side of the stacker 21 to separate the sheets each other, then the sheet bundle S is placed on the stacker 21 to register the sheet bundle S in the longitudinal direction. Therefore, a moving area of the aligning member 24 can be minimized and it is not necessary to extend the stacker 21 in the oblique direction. Thus, besides the size increase of the stacker 21 can be suppressed, increase in size of the post-processing apparatus can be suppressed and cost thereof can be reduced.

Generally speaking, the sheet on which an image is formed often keeps the heat of the fixing process. In the present embodiment, the air exhausted from the blower section 3 contacts with the sheet, thus there is a merit that the sheet can be cooled down quickly.

It is to be understood that changes and variations of the present embodiment may be made without departing from the spirit or scope of the appended claims.

For example, in case a coated sheet is used, even if the sheet size is smaller than the standard size, by switching the blower section 3 from off to on, the sheet bundle can be registered in the longitudinal direction using the blower section 3. In the above method, the coated sheets tend to stick each other can be unfailingly separated irrespective of the sheet size and a highly accurate register can be ensured.

In the present embodiment, in Step ST2, whether or not the sheet size is greater than the standard size is judged based on information inputted from the operation display section O. Instead of the information inputted from the operation display section O, whether or not the sheet size is greater than the standard size can be judged from a time interval between the sheets in the conveyance path a by using the sensor section 28. In the above case, for example, the longer interval between the sheets conveyed in the conveyance path a can be judged to be a larger sheet size.

Also, in the present embodiment, while the blower section 3 is used to maintain the accuracy of register in the stacker in which the post-processing is carried out, the blower section can be disposed at a position from which air is blown against the sheet ejected from the ejected sheet tray T so as to enhance the accuracy of register of the final ejected matter using the stacker as the ejected sheet tray.

According to the present embodiments, ability of register of the recording material bundle can be enhanced while preventing the configuration of the apparatus from growing in size. 

1. A post-processing apparatus, comprising: a stacker obliquely disposed to stack a recording material bundle; and a blower section disposed at a lower end side of the stacker to blow air from the lower end side to an upper end side of the stacker towards an edge section of a recording material being sliding down on a stacking surface of the stacker.
 2. The post-processing apparatus of claim 1, further comprising a stopper to contact with an edge section of the recording material bundle to be stacked on the stacking surface, wherein the blower section continues to blow air within a time period from when the recording material is conveyed to the stacker to at least when the edge section of the recording material comes in contact with the stopper.
 3. The post-processing apparatus of claim 1, further comprising a control section to control the blower section so as to blow air in a case when a recording material size exceeds a standard size.
 4. The post-processing apparatus of claim 1, further comprising a control section to control the blower section so as to blow air in accordance with type, basis weight, number or size of the recording material.
 5. The post-processing apparatus of claim 1, further comprising a push down member supported in a rotatable manner around an axis to push down a rear edge of the recording material to be conveyed to the stacker towards the stacking surface.
 6. The post-processing apparatus of claim 1, further comprising a post-processing section to apply post-processing to the recording material stacked on the stacker.
 7. An image forming system, comprising: an image forming apparatus to from an image on the recording material, and the post processing apparatus of claim 1 to convey the recording material, on which the image has been formed by the image forming apparatus, and to apply post-processing to the recording material.
 8. The image forming system of claim 7, further comprising a stopper to contact with the edge section of the recording material bundle to be stacked on the stacking surface, wherein the blower section continues to blow air within a time period from when the recording material is conveyed to the stacker to at least when the edge section of the recording material bundle comes in contact with the stopper.
 9. The image forming system of claim 7, further comprising a control section to control the blower section so as to blow air in case a recording material size exceeds a standard size.
 10. The image forming system of claim 7, further comprising a control section to control the blower section so as to blow air in accordance with type, basis weight, number or size of the recording material.
 11. The image forming system of claim 7, further comprising a push down member supported in a rotatable manner around an axis to push down a rear edge of the recording material to be conveyed to the stacker towards the stacking surface.
 12. The image forming system of claim 7, further comprising a post-processing section to apply post-processing to the recording material stacked on the stacker. 